package com.znyj.servlet.utilsTool;

/**
 * Created by gaoliwei02 on 2017/9/22.
 */

import javax.crypto.Cipher;
import java.security.Key;
import java.security.Security;

public class DesUtil {

    private static String strDefaultKey = "simple";
    private static Cipher encryptCipher = null;
    private static Cipher decryptCipher = null;

    public static void init() throws Exception {
        Security.addProvider(new com.sun.crypto.provider.SunJCE());
        Key key = getKey(strDefaultKey.getBytes());

        encryptCipher = Cipher.getInstance("DES");
        encryptCipher.init(Cipher.ENCRYPT_MODE, key);

        decryptCipher = Cipher.getInstance("DES");
        decryptCipher.init(Cipher.DECRYPT_MODE, key);
    }

    public static String encrypt(String strIn) throws Exception {
        return byteArr2HexStr(encrypt(strIn.getBytes()));
    }
    public static String decrypt(String strIn) throws Exception {
        return new String(decrypt(hexStr2ByteArr(strIn)));
    }

    //从指定字符串生成密钥，密钥所需的字节数组长度为8位 不足8位时后面补0，超出8位只取前8
    private static Key getKey(byte[] arrBTmp) throws Exception {
        // 创建一个空的8位字节数组（默认值为0）
        byte[] arrB = new byte[8];

        // 将原始字节数组转换为8位
        for (int i = 0; i < arrBTmp.length && i < arrB.length; i++) {
            arrB[i] = arrBTmp[i];
        }

        // 生成密钥
        Key key = new javax.crypto.spec.SecretKeySpec(arrB, "DES");

        return key;
    }

    //将byte数组转换为表示16进制值的字符串， 如：byte[]{8,18}转换为：0813， 和public static byte[]hexStr2ByteArr(String strIn) 互为可逆的转换过程
    public static String byteArr2HexStr(byte[] arrB) throws Exception {
        int iLen = arrB.length;
        // 每个byte用两个字符才能表示，所以字符串的长度是数组长度的两倍
        StringBuffer sb = new StringBuffer(iLen * 2);
        for (int i = 0; i < iLen; i++) {
            int intTmp = arrB[i];
            // 把负数转换为正数
            while (intTmp < 0) {
                intTmp = intTmp + 256;
            }
            // 小于0F的数需要在前面补0
            if (intTmp < 16) {
                sb.append("0");
            }
            sb.append(Integer.toString(intTmp, 16));
        }
        return sb.toString();
    }

    //将表示16进制值的字符串转换为byte数组， 和public static String byteArr2HexStr(byte[] arrB)互为可逆的转换过程
    public static byte[] hexStr2ByteArr(String strIn) throws Exception {
        byte[] arrB = strIn.getBytes();
        int iLen = arrB.length;

        // 两个字符表示一个字节，所以字节数组长度是字符串长度除以2
        byte[] arrOut = new byte[iLen / 2];
        for (int i = 0; i < iLen; i = i + 2) {
            String strTmp = new String(arrB, i, 2);
            arrOut[i / 2] = (byte) Integer.parseInt(strTmp, 16);
        }
        return arrOut;
    }

    //加密字节数组
    public static byte[] encrypt(byte[] arrB) throws Exception {
        return encryptCipher.doFinal(arrB);
    }

    //解密字节数组
    public static byte[] decrypt(byte[] arrB) throws Exception {
        return decryptCipher.doFinal(arrB);
    }

//    /**
//     * main方法  。
//     *
//     * @param args
//     * @author 刘尧兴
//     */
//    public static void main(String[] args) {
//        try {
//            String test = "123456789";
//            DesUtils des = new DesUtils("leemenz");//自定义密钥
//            System.out.println("加密前的字符：" + test);
//            System.out.println("加密后的字符：" + des.encrypt(test));
//            System.out.println("解密后的字符：" + des.decrypt(des.encrypt(test)));
//
//            System.out.println("解密后的字符：" + des.decrypt("202cb962ac59075b964b07152d234b70"));
//        } catch (Exception e) {
//            e.printStackTrace();
//        }
//    }
}

